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Hierarchical design organizes and modularizes any design. In schematic capture, hierarchical blocks and sub-circuits are common practices (to learn more about hierarchical blocks click here), however at PCB layout the process is not as well documented.
In this article we will follow a simple step-by-step process in order to re-use and repeat circuit elements at a PCB level, in order to make our final design quicker and easier. This same process can be used for panelization to copy and re-use an entire board design multiple times in a single Ultiboard file for manufacturing purposes.
Imagine a design in which you have eight digital synthesizer circuits. Each synthesizer circuit has the exact same components (resistors, capacitors, and logic chips). At a schematic level in NI Multisim, you would create a Hierarchical Block which contained this design, which could be easily copied and re-used as many times as necessary (eight in this example).
As the board is prepared for layout in Ultiboard we can also similarly layout, route and configure "PCB modules" which can then be copied and re-used readily to effectively compete a board-level design. In many cases each of these PCB modules represents a Hierarchcial Block in Multisim.
Therefore if one was to create a Hierarchical Block in Multisim which contained a resistor and capacitor), you could use it multiple times in a design. Therefore:
Basically by copying and pasting HB1 multiple times, you can reduce the time and effort to complete a schematic.
As you transition to Ultiboard and layout, each of these hierarchical blocks will be represented in their landpattern (or footprint) form. Therefore again you will want to reduce the work and time involved with the design, by taking the elements of hierarchical block 1 (HB1), configuring placement and defining the copper traces, and then effectively copying and pasting these elements. The most effective manner in which to repeat common PCB circuit elements in Ultiboard consists of four steps:
Prepare for this example by opening NI Ultiboard. You can find Ultiboard at Start > All Programs > National Instruments > Circuit Design Suite 11.0 > Ultiboard.
The first step is to create a unique Ultiboard Part Group which represents each PCB module (in this example we would need 8 seperate Part Groups, to represent each digital synthesizer module). A Part Group effectively creates an association between various components in a design and allows you as a designer to give this group a unique identifier.
We can now create a unique group for each PCB design module.
Figure 1: Creating a Part Group
There are two methods with which to assign parts to a group. We will investigate both. It is recommended that you use the second method due to it being easier.
You may have noticed that after defining the group name in the Edit Group dialog box, you can Assign Parts directly to a group name (within the same dialog). This is certainly a method that you can use, by:
Another method that one can use, that further simplifies this part association task is to the use the Spreadsheet View in Ultiboard. Ultiboard is a tabular representation of all components within the workspace. It effectively captures all pertinent information about components and trace on a design (name, value, spacing, pin properties) in one simple, easy-to-use interface. The Spreadsheet View also allows you to view the Part Group that each component is assigned to within a design. Therefore we can use use the Spreadsheet view.
Figure 2: Using the Spreadsheet View to Assign Parts
Using the various placement and routing tools in Ultiboard, define the placement and routing of a group of PCB circuit elements that belong to a group (for example all the components that you have assigned to group synth_1).
With the first group (synth_1 for example) completed we can begin replicating the careful placement and routing for all other groups in the design. Basically what we can do is take the placement (part orientation) and exact copper routing configuration and apply them to the other part groups that we have defined.
Figure 3: Group Replication
We can now begin replicating the copper traces for each of these PCB modules or Part Groups and apply it to another group.
Figure 4: Copy Route
With these four simple steps you are able to effectively copy and place identical PCB design modules, to make the layout and routing process quicker, easier and more effective. You can see a simple example of the results of the above four step process in figure 5 below.
Figure 5: Completed Design
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